Separating alkyl benzenes from admixture with paraffins and naphthenes



Patented Mar. 15, 1949 SEPARATING ALKYL BENZENES FROM AD- MIXTURE VJITH PARAFFINS AND NAPH- THEN ES Orland M. Reiff, Woodbury, N. 5., and Alexander M. Moore, Baltimore, Md, assignors to Socony- Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Application September 14, 1944, Serial No. 554,162

4 Claims. 1

This invention relates to a method for separating aromatic hydrocarbons from aromatic petroleum stocks and to the production of alkylhaloaralkyl halides from petroleum and derivatives thereof.

It is well known in the art that certain petroleum stocks, hereinafter referred to as aromatic petroleum stocks, contain relatively large amounts of aromatic hydrocarbons. These stocks are mixtures of acyclic, alicyclic and carbocyclic hydrocarbons. In the interest of brevity, hereinafter the acyclic and alicyclic constituents Will be referred to as non-aromatic hydrocarbons and the carbocyclic components of the mixture will be referred to as aromatic hydrocarbons. Substantial portions of these aromatic hydrocarbons are present as alkylated aromatic hydrocarbon compounds in varying degrees of alkylation.

Separation and recovery of aromatic hydrocarbons from these aromatic petroleum stocks, by fractional distillation, is precluded by overlapping boiling points of the aromatic hydrocarbons and of the non-aromatic hydrocarbons present in stocks, and by pseudo-azeotropic efiects. Separation and recovery by other physical methods, such as solvent treatment, selective adsorption and the like, involve many practical difficulties. Recourse to chemical methods for effecting an efficient separation and recovery of the aromatic hydrocarbons from the aromatic petroleum stocks, likewise has proved difficult,

due primarily to the lack of specificity of most chemical reactions.

While this invention provides a means of separating aromatic hydrocarbons from non-aromatic hydrocarbons of substantially the same boiling point whatever may be the molecular weight and the boiling point of the hydrocarbon compounds, the principles of this invention are most easily disclosed and taught by describing the process of this invention as applied to the separation of alkyl-benzenes from non-aromatic materials of substantially the same boiling point.

The chlorination of a pure alkyl-benzenes, for example, toluene and some of its homologues to obtain exclusively either nuclear or side chain chlorination at will has been known to chemists for many years. In fact, chlorobenzyl chloride has been prepared by chlorinating toluene first under one set of conditions and then the other. It is to be noted however, that a process for the chlorination of so complex a mixture as the aromatic petroleum stocks to obtain uncontaminated alkylchlorobenzyl chlorides has not been stocks include polyalkylbenzenes whose nuclei are extremely reactive with respect to substitution reactions when comparedwith benzene and toluene, and it is difficult to prevent these nuclei from reacting with electrophilic reactants capable of attacking the benzene ring. In the side chain chlorination of aromatic petroleum stocks, two such reactants are present, chlorine and polyalkylbenzyl chlorides. Under the conditions of side chain chlorination both of these reactants attack the reactive nuclei, thereby greatly reduc-,

ing the yields of alkylbenzyl chlorides obtainable from the reaction. When an attempt is made to chlorinate aromatic petroleum stocks for the purpose of obtaining alkylbenzyl chlorides directly in one step, only low yields of impure products are obtained.

The present process provides a means for obtaining alkylhaloralkyl halides having many of the valuable properties of the alkylbenzyl chlorides, together with additional desirable properties but with the great advantage of avoiding the two difliculties mentioned hereinbefore.

It is an object of this invention to provide a process for separating aromatic compounds from non-aromatic compounds of substantially the same boiling point. Another object of this invention is to provide a means for separating alkylbenzenes from paraffins and naphthenesof substantially the same boiling point. A further object of this invention is to provide a means for producing alkylhaloaralkyl halides and particularly alkylchlorobenzyl chlorides. Other objects and advantages will become apparent from the following description. u

In accordance with the principles of this inven: tion, the alkylated aromatic compounds may be separated from non-aromatic substances such as In fact, it has thus far' the praflins and the naphthenes or hydroaromatic compounds. In general, a fraction of the mixture of aromatic and non-aromatic compounds is selected in which substantially none of the non-aromatic compounds have a boiling point within the boiling range of the nuclear halogenated aromatic compounds formed in the halogenation reaction. That is to say, a fraction of the aromatic stock is selected to have no compounds of boiling points appreciably higher than the boiling point of the highest boiling aromatic compound. Nuclear halogenation then gives alkylhalo aromatic compounds which may be easily separated from the unhalogenated hydrocarbons by distillation. The halogen atom on the aromatic ring apparently deactivates the ring to such an extent that on subsequent halogenation, the reaction between the ring and the alkylhaloaralkyl chloride formed is greatly decreased. Furthermore, the reaction between the ring of the aromatic compound and the halogen is greatly decreased and a product is obtained which contains two halogen atoms per molecule, one of which is on the ring and the other on the side chain of the aromatic compound. Nuclear chlorination is carried out at temperatures of about 15 C. to about 35 C. in the presence of a catalyst and the side chain chlorination is carried out at about 100 C. to about 160 C. with illumination.

The alkylhaloaralkyl halides obtainable by the method outlined hereinbefore are valuable as intermediates for the easy preparation of a great number of materials. Thus, the side chain halogen may be replaced by the appropriate functional group to give thiocarbonates, xanthates, cyanides, thiocyanates, alcohols, thioalcohols, ethers, thioethers, disulfides, nitriles, esters, amines, amides, acids, etc. The products may be employed in the manufacture of dyes. pharmaceuticals, resins, plasticizers, insecticides, fungicides and mineral oil additives.

Thos skilled in the art know that the aromatic compounds having nine carbon atoms in the molecule have a possible boiling range of 155 C. to 200 C. When treating aromatic petroleum stocks it is preferred to subject the aromatic petroleum stock to fractional distillation to obtain a fraction containing substantially only aromatic compounds having nine carbon atoms in the molecule. For this purpose, when fractionating an aromatic petroleum stock to obtain starting material for the preparation of alkyl halobenzyl halides and the separation of the C9 aroma-tic from the non-aromatic portion of the aromatic petroleum stock, a fraction boiling within the range of about 160 C. to about 175 C. is preferred.

Illustrative of this invention is the followin example which has been provided for the guidance of those skilled in the art and is not limit- An aromatic petroleum stock, generally available under the trade name Sovasol #75 was fractionated through a 15 plate column at a re-' flux ratio of 10:1. The fraction boiling at 160.5 C. to 173.0 C. at atmospheric pressure was chlorinated at room temperature employing a catalyst (both iron and iodine are satisfactory as catalysts in this chlorination) to introduce one chlorine atom into the nucleus of the alkyl aromatic compounds present in the fraction. As those skilled in the art know, nuclear halogenation can be carried out at room temperature (about 15 C. to about 35 C.) with diffused or no light and in the presence of a catalyst such as iodine, iron, phosphorus, sulfur and iron or aluminum halides, especially the chlorides and bromides. After the friction had been chlorinated to the extent that one atom of chlorine had reacted for each molecule of alkyl benzene present, the mixture of chlorinated alkylbenzenes and non-chlorinated nonaromatic materials was fractionated and a liquid monochloro-fraction separated. When it is desirable to obtain the alkyl aromatics as such, the chlorinated alkyl aromatic can be treated in any suitable manner known to those skilled in the art to dechlorinate or dehalogenate the alkyl aromatic. However, when it is desired to produce alkylchlorobenzyl chlorides, the liquid monochlorcfraction so produced is chlorinated at about C. to about 160 C. and preferably, at about C. to about C. and particularly, at about 140 C.:2 C. in bright light such as that provided by one 200-watt and one 100-watt tungsten lamps until the specific gravity of the mixture reaches the value of d4 =1.200. Under these conditions the nuclearly chlorinated or halogenated aromatic compounds are chlorinated or halogenated in the side chain. The reaction mixture was blown with nitrogen or another inert gas to re move hydrochloric acid and fractionated through a Vigreaux column at 2.5 mm. of pressure. By distilling the reaction mixture obtained by chlorinating the alkyl monochlorobenzenes obtained in the first step, the following fractions were obtained from 1223 grams of reaction mixture:

Fraction Analysis of the dichloride and trichloride for total and side chain chlorine showed that no measurable amount of chlorine entered the nucleus in the second step. Apparently the presence of one atom of chlorine in the nucleus inhibited further nuclear chlorination to such an extent that the alkylmonochlorobenzyl chlorides were produced free of alkyl dichlorobenzenes, and the methylchloroxylylene dichlorides were free of isomers containing two moles of nuclear chlorine. This was true in spite of the fact that in the one step chlorination of meta-xylene, for example, even the conditions most favorable to side chain chlorination resulted in at least ten per cent of the reacting chlorine entering the nucleus when chlorine gas was used as the chlorinating agent.

When the reaction and distillation temperatures were kept below C., these appeared to be no tendency for the product to react With itself in a polymerization like reaction with loss of HCl. In those cases in which the temperature did rise above 160 C., however, or when sufficient quantities of iron, zinc, aluminum, or other Friedel and. Crafts catalysts were present, noticeable polymerization did occur.

Since the aromatics in Sovasol #75 are largely polymethyl benzenes, the products obtained in Example 1 were quite pure dimethylchlorobenzyl chlorides and methylchloroxylylene dichlorides. To our knowledge these products have not been previously prepared in such-a degree oi -purity;

their physical properties are therefore given below.

When the alkylmonochlorobenzene is to be further chlorinated to obtain alkylchlorobenzyl chlorides, it is advantageous to separate crystalline 5-chloropseudocumen from the other alkylchlorobenaenes in any suitable manner, for example, by filtration to facilitate fractionation after the side chain chlorination of the alkyl monochloro benzenes.

While the procedure described hereinbefore in Example 1 produces nuclear monochloro aromatics, aromatic petroleum stocks can be chlorinated or halogenated to give diand trichloroor haloaromatics. The diand trichloro-aromatics are solids which can be purified by crystallization instead of by distillation. These polychlorinated or pclyhalogenated aromatics can be con- Verted to the corresponding chloroaralkyl chlorides or haloaralkyl halides by the procedure of the second part of Example 1.

An aromatic petroleum stock generally available under the trade name "SovasoP #75 has been used herein to illustrate the principles of the invention. Sovasol #75 is a generic term connoting aromatic petroleum stocks derived from Houdry cracking operations. These stocks have boiling point ranges varying between 150 C. and 210 C. and ordinarily contain between 50% and 75% aromatic hydrocarbons and the balance nonaromatic hydrocarbons, depending upon the source of the Eoudry cracking stock and the severity of the cracking procedure in the Houdry units. The aromatic hydrocarbons that occur in Sovasol #75 stocks are believed to be primarily, polymethyl benzenes ranging from trimethyl benzene to tetramethyl benzene. It is possible that small amounts of other aromatic hydrocarbons, such as ethylmethyl benzene may be present also. There are three trimethyl benzenes, mesitylene or 1,3,5- trimethyl benzene; pseudocumene or 1,2,4-trimethyl beacne; and hemimellitine or 1,2,3-trimethyl benzene. Likewise, there are three tetramethyl benzenes, durene or l,2,4,5-tetramethyl benzene; isodurene or 1,2,3,5-tetramethyl benzene; and prehuitine or 1,2,3fi-tetramethyl benzene. The trimethyl benzenes constitute the predominant portion oi the polyalkylated benzenes present in Sovasoi #75 stocks. For example, if a Sovasol #75 stock containing 55% aromatic hydrocarbons, is subjected to distillation, the fraction boiling between 150 C. and 182 C. will contain 60% aromatic hydrocarbons and will constitute 75% of the original Sovasol #75 stock. This temperature range (150 C.-l82 C.) includes the boiling points of the trimethyl benzenes, but does not include the boiling points of the tetramethyl benzenes. Stated differently, the 75% distillate contains about 82% of the aromatic hydrocarbons originally present in the Sovasol #75 stock, that boil Within the boiling range of trimethyl benzenes.

We claim:

1. A process for separating alkyl benzenes having nine carbon atoms from other alkyl benzenes and non-aromatic materials which comprises subjecting a hydrocarbon mixture containing alkyl benzenes hayingnine carbon atoms in the molecule and other aromatic and non-aromatic compounds to fractional distillation, separating a fraction having a boiling range ot-about 160.'5 =C. to about 173.0 C. at atmospheric pressure, nucleaIlY dlogenating said fraction at a temperature 7 between about 15 C. and about 35 C. in the presence of a catalyst to introduce one halogen atom an aromatic petroleum stock to fractional distillation to obtain a fraction boiling between about 160.5 C. and 173.0 C. at atmospheric pressure; chlorinating said fraction at a temperature between about 15 C. and about 35 C. in the presence of a catalyst to introduce one chlorine atom into each benzene nucleus; subjecting said chlorinated fraction to fractional distillation to separate therefrom fraction having a boiling point of about 62 C. to about 76 C. at 2.5 mms. pressure.

3. A process for producing alkylchlorbenzyl chlorides, which comprises: subjecting an aromatic petroleum stock to fractional distillation to obtain a fraction containing alkyl benzenes and non-aromatic hydrocarbons, said fraction having a boiling range of about 1605 C. to about 1'73.0 C. at atmospheric pressure; chlorinating said fraction at a temperature between about 15 C. and about 35 C. in the presence of a catalyst to introduce one chlorine atom into each benzene nucleus; subjecting said chlorinated fraction to fractional distillation to separate therefrom a fraction having a boiling point of about 62 C. to about 76 C. at 2.5 mms. pressure; chlorinating said last-mentioned fraction at a temperature between about 138 C. and about 142 C. in the presence of light until the specific gravity of the resulting reaction mixture attains the value of (14 :1200; removing residual hydrochloric acid from said reaction mixture; and subjecting said reaction mixture to fractional distillation to obtain said alkylchlorbenzyl chlorides.

4. A process for producing alkylchlorbenzyl chlorides, which comprises: subjecting an aromatic petroleum stock to fractional distillation to obtain a fraction containing alkyl benzenes and non-aromatic hydrocarbons, said fraction having a boiling range of about 160.5 C. to about 173.0 C. at atmospheric pressure; chlorinating said fraction at a temperature between about 15 C. and about 35 C. in the presence of a catalyst to intro duce one chlorine atom into each benzene nucleus; subjecting said chlorinated fraction to fractional distillation to separate therefrom a fraction having a boiling point of about 62 C. to about 76 C.

2.5 mms. pressure; chlorinating said last-mentioned fraction at a temperature between about 106 C. and about 160 C. in the presence of light until the specific gravity of the resulting reaction mixture attains the value of d4 =1.200; removing residual hydrochloric acid from said reaction mixture; and subjecting said reaction mixture to fractional distillation to obtain a fraction comprising said alkylchlorbenzyl chlorides and having a boiling point of about C. to about C. at 2.5 mms. pressure.

ORLAND M. REIFF.

ALEXANDER. M. MOORE.

(References on following page) Number REFERENCES CITED 1,741,305 The following references are of record in the 1,734,267 file of this patent: 1,828,858 UNITED STATES PATENTS 5 12,218,148

Number Name Date 1,219,166 Schmidlin Mar. 13, 191'! 1,248,065 Blane Nov. 27, 1917 8 Name Date J aeger Dec. 31, 1929 Britten et a1 Dec. 9, 1930 Conklin Oct. 27, 1931 Hardie Oct. 15, 1940 OTHER REFERENCES Ellis: Chemistry of Petroleum Derivatives, vol. I, (1934), PP. 768-780.

Certificate of Correction Patent No. 2,464,769. March 15, 1949,

ORLAND M. REIFF ET AL.

It is hereby certified. that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 45, for alkyl-benzenes read alkyl-benzene; column 2, line 36, for alkylhaloralkyl read alkylhaloamllcyl; column 4, line 4, for the word friction read fraction line 63, for these read there; column 5, line 8, in the table, first column thereof, for Refractive Index, 12 read Refractive Index, n

and thatthe said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of October, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommiasa'oner of Patents.

Certificate of Correction Patent No. 2,464,769. March 15, 1949,

ORLAND M. REIFF ET AL.

It is hereby certified. that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 45, for alkyl-benzenes read alkyl-benzene; column 2, line 36, for alkylhaloralkyl read alkylhaloamllcyl; column 4, line 4, for the word friction read fraction line 63, for these read there; column 5, line 8, in the table, first column thereof, for Refractive Index, 12 read Refractive Index, n

and thatthe said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of October, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommiasa'oner of Patents.

Certificate of Correction Patent No. 2,464,769. March 15, 1949,

ORLAND M. REIFF ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 45, for alkyl-benzenes read ethyl-benzene; column 2, line 36, for alkylhaloralky read alkylhaloamlkyl; column 4, line 4, for the word friction read fraction line 63, for these read there; column 5, line 8, in the table, first column thereof, for Refractive Index, n read Refractive Index, n

and thatthe said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of October, A. D. 1949.

THOMAS F. MURPHY,

Aaaiatant Ounnniem'oner of Patents. 

